#include <stdio.h>
#include <sys/types.h>
#include <dirent.h>
#include <sys/stat.h>
#include <string.h>
 
void do_ls(char[]);
void dostat(char *);
void show_file_info( char *, struct stat *);
void mode_to_letters( int , char[] );
char * uid_to_name( uid_t );
char * gid_to_name( gid_t );
 
 
main(int ac, char *av[])
{
    if( ac == 1 )
    do_ls( "." );          /*显示当前目录*/
    else
    while( --ac ){
        printf("%s:\n", *++av);   /*显示参数指定的目录*/
        do_ls( *av );
    }
}
 
 
void do_ls( char dirname[] )
{
    DIR *dir_ptr;
    struct dirent *direntp;
 
    if( (dir_ptr = opendir( dirname )) == NULL)            /*打开目录,成功则返回 DIR 结构指针*/
    fprintf(stderr, "ls1: cannot open %s\n", dirname);
     
    else
    {
    while( ( direntp = readdir( dir_ptr ) ) != NULL )
         dostat( direntp->d_name );
 
    closedir( dir_ptr );
    }
}
 
void dostat( char *filename )
{
    struct stat info;
 
    if( stat( filename, &info ) == -1 )
    perror( filename );
    else
    show_file_info( filename, &info );
}
 
void show_file_info( char *filename, struct stat *info_p )
{
 
    char *uid_to_name(), *ctime(), *gid_to_name(), *filemode();
    void mode_to_letters();
 
    char modestr[11];
 
    mode_to_letters( info_p->st_mode, modestr );      /*模式到字符的转换*/
 
    printf("%s", modestr );                           /*输出模式标识符*/
 
    printf("%4d", (int)info_p->st_nlink);
 
    printf(" %-8s", uid_to_name(info_p->st_uid));
 
    printf("%-8s", gid_to_name(info_p->st_gid));
 
    printf("%8ld  ", (long)info_p->st_size);
 
    printf("%.12s ", 4 + ctime(&info_p->st_mtime));
 
    printf("%s\n",filename);    
 
}
 
 
void mode_to_letters( int mode, char str[] )
{
    strcpy(str,"----------");
 
    if( S_ISDIR(mode) ) str[0] = 'd';                 /*目录*/
    if( S_ISCHR(mode) ) str[0] = 'c';                 /*字符文件*/
    if( S_ISBLK(mode) ) str[0] = 'b';                 /*块文件*/
 
    if(mode & S_IRUSR)  str[1] = 'r';
    if(mode & S_IWUSR)  str[2] = 'w';
    if(mode & S_IXUSR)  str[3] = 'x';
     
    if(mode & S_IRGRP)  str[4] = 'r';
    if(mode & S_IWGRP)  str[5] = 'w';
    if(mode & S_IXGRP)  str[6] = 'x';
 
    if(mode & S_IXOTH)  str[7] = 'r';
    if(mode & S_IXOTH)  str[8] = 'w';
    if(mode & S_IXOTH)  str[9] = 'x';
}
 
#include <pwd.h>
 
    char *uid_to_name( uid_t uid )
/*
*返回和 uid 相应的用户名的指针
*/
    {
    struct passwd *getpwuid(), *pw_ptr;
    static char numstr[10];
 
    if( ( pw_ptr = getpwuid( uid ) ) == NULL ) {
        sprintf(numstr, "%d", uid);      /*没有对应的用户名则 uid 存入 numstr,返回后以字符串的形式打印 uid*/
        return numstr;
    }
    else
        return pw_ptr->pw_name;          /*打印用户名*/
    }
 
 
#include <grp.h>
 
    char *gid_to_name( gid_t gid )
    {
    struct group *getgrgid(), *grp_ptr;
    static char numstr[10];
 
    if( ( grp_ptr = getgrgid(gid) ) == NULL ){
 
        sprintf(numstr, "%d", gid);
        return numstr;
    }
    else
        return grp_ptr->gr_name;
    }
